I. Field of the Invention
This invention relates to a method of and an apparatus for manufacturing a panel of a cathode ray tube and, more particularly, to a method of manufacturing a phosphor screen by bonding phosphor particles on a powder-receptive adhesive pattern formed on the inner surface of a panel, and an apparatus therefor.
II. Prior Art
Heretofore, there is known a photo-adhesive method (disclosed in Japanese patent Disclosure No. 58-89751) as a method of manufacturing a phosphor screen on the inner surface of a panel of a color cathode ray tube. This method features the steps of coating a photosensitive composition which becomes adhesive upon the irradiating of a light thereon, on the inner surface of a panel of a cathode ray tube, drying the composition, then mounting a shadow mask on the panel, irradiating a light, through the apertures of the shadow mask, onto that portion of the photo-sensitive composition layer in which phosphor picture elements are to be formed, thereby forming a powder-receptive adhesive pattern. Then, phosphor powder is applied to the inner surface of the panel, for it to adhere to the adhesive pattern, the excess phosphor powder not adhering thereto is removed, and eventually developing the phosphor powder, thereby removing the photo-sensitive composition layer of that portion onto which the light is not irradiated. This series of steps, consisting of exposure, phosphor application, and development is repeated for first color, second color, and third color, so as to thereby manufacture a phosphor screen composed of three color phosphor picture elements. In the process of applying the phosphor powder to the inner surface of the panel, the powder is fed thereto by a separately provided powder-feeding device, the panel is rocked in X and Y directions by a rocking device, so as to slide the phosphor powder, in a zigzag manner, over the inner surface thereof, whereby the phosphor powder adheres to the adhesive pattern. Thereafter, the panel is inverted, and the excess, i.e., non-adhering phosphor powder is recovered.
However, the above-mentioned method has following drawbacks:
The phosphor powder sometimes adheres unevenly to or separates from the phosphor screen. A long period of time is required for the phosphor powder to adhere to the screen, and a large quantity of powder is scattered in the air when the excess phosphor powder is recovered. Further, an apparatus is required for recovering the excess phosphor powder thereby increasing the size and complexity of the overall powder-application/-recovery apparatus.
Another method of manufacturing a phosphor screen is disclosed in Japanese patent Disclosure No. 59-117041. This method features the steps of forming an adhesive pattern on the inner surface of a panel of a color picture tube, as in the case of the above-mentioned similar method, positioning the panel such that an adhesive pattern-forming surface is provided on the lower surface thereof, introducing the phosphor powder by means of an air flow from below, and adhering the phosphor powder to the adhesive pattern while moving on the inner surface of the panel. According to this method, it is not necessary to provide an apparatus for recovering the excess phosphor powder. On the other hand, the drawbacks of the previously-described conventional method, i.e., the increased complexity of the phosphor powder-application/-recovery apparatus, and the uneven adhering of the phosphor powder to the phosphor screen, also arise in the case of this method.
A method whereby the drawbacks of the abovementioned methods are eliminated is disclosed in Japanese patent Disclosure No. 60-207229. This method features the steps of positioning a panel such that the adhesive pattern-forming surface is directed upward, applying phosphor powder to the inner surface of the panel while rotating the panel about an axis passing through the center thereof, to allow the powder to slide on the inner surface of the panel and to adhere to the adhesive pattern. Using this method, the incidence of phosphor powder adhering unevenly is reduced. However, another drawback arises in that the thickness of the phosphor layer is less at the periphery that at the center of the panel. Since it is necessary, according to this method, to rotate the panel about an inclined axis, this gives rise to such drawbacks as the increased complexity of the phosphor powder-application/-recovery apparatus and the consequent large amount of space required for the installation of this apparatus.
In any of the above-mentioned methods, the phosphor powder is agglomerated in the case of the certain sort of the phosphor powder to cause the phosphor screen to become uneven. This is particularly inconvenient when this is applied to a small-sized picture tube.